There is a pond on my way home from work, which I sometimes stop and sit beside. It is filled with millions and millions of tiny fish.

Most of the fish are very skinny. They spend eight or more hours a day searching for food, and it is barely enough. The pond also contains several leaches. A half dozen of them have grown to incredible size, by mercilessly siphoning the blood of all the fish in the pond. Some of the smaller leaches only take enough blood to keep themselves alive, but the giant leaches are so bloated they no longer worry about the fish. They just sit on the bottom of the pond, draining any fish foolish enough to swim near them.

One of them, whom I have named the Royal Leach, is larger than any other. Its eyes now protrude over the surface, and it can see into neighbouring ponds.

It is not as big as some of the leaches in those ponds, and it is jealous. As I sit and watch, it joins with another giant leach, so together they will be as big as the corpulent mega-leaches in other ponds. Lost in the shadows of their own stolen blood, the fish are getting even skinnier. Some of them float to the surface, dead. The giant leaches are too wrapped up in their own insecurity to notice.

They have forgotten that the parasitic relationship is symbiotic, and so they drain their hosts dry. There are toads in the pond, who earlier in the year set limits on how much blood the leaches could take. Now they are afraid of being crushed, so they hide in their corner of the pond and pretend they're still in control.

The fish are still struggling to find enough food for themselves and their uninvited guests. They work harder and harder, but become weaker and scrawnier each day.

A thickening layer of dead fish obscures the pond. The stench of it is almost intolerable. I can't stand to sit beside the pond anymore. As I ride past, I wonder if there are still fish in the pond, struggling to stay alive.

But the sun is setting, and all I can see is the bank across the street reflected on the surface.